Accident Disease Case Study And Underlying Cause
Karla Van den Broek and Rik Op De Beeck, Prevent, Belgium
A major concern of safety at work is preventing accidents at work. An accident at work can be defined in different ways depending of the context in which it is used. Often also the word incident is used, sometimes as a broader term encompassing ‘an accident' as a specific type of incident, but sometimes the words accidents and incidents refer to two different types of events.
Prevention of accidents at work focuses on the causes of accidents. Accident causation models provide a theoretical basis for explaining how accidents at work occur. Statistical data give some details about the accidents that occur in the workplace: the occurrence, the victims and the causes.
Definitions of accidents and incidents
Numerous definitions exist of accidents and incidents at work. The nature of the definitions often depends on the context and the purpose such as accident prevention (1.1), workers' compensation (1.2) and statistics (1.3).
The definition of an accident at work in the context of accident prevention
In the context of accident prevention, the phenomenon of accidents and incidents are often viewed in light of accident investigation and analysis. The main purpose is to gain insight in the (underlying) causes in order to prevent accidents in the future and to improve the safety of the workers. Definitions of accidents and incidents reflect this purpose and refer one way or another on how accidents occur.
The definition of an accident provided by Heinrich in the 1930s is often cited. Heinrich defines an accident as an unplanned and uncontrolled event in which the action or reaction of an object, substance, person or radiation results in personal injury or the probability thereof. Variations on this definition can be found throughout the safety literature. Bird and Germain for instance define an accident as an unintended or unplanned happening that may or may not result in property damage, personal injury, work process stoppage or interference, or any combination of these conditions under such circumstances that personal injury might have resulted.
In more recent literature, it is often argued that the notions "unplanned", "uncontrolled" are misleading. This might give the idea that the event is related to fate or chance. It can't be controlled. However, when the causes are determined, it is usually found that many events were predictable and could have been prevented if the right actions were taken. This implies that the event is not one of fate or chance.
Most contemporary definitions don't include the notion "unplanned" and/or speak in more general terms of "incident" instead of accident. The OHSAS 18001 standard focuses on the definition of an incident. An incident is referred to as a work-related event(s) in which an injury or ill health (regardless of severity) or fatality occurred, or could have occurred. An accident is regarded as a particular type of incident in which an injury or illness actually occurs. A near-miss is an incident where no injury or illness occurs. Therefore, an incident can be either an accident or a near-miss.
Although the term incident is regarded more and more as a broad term encompassing all events causing injury or material damages and also near-miss events, this is not always the case. Incident is often also referred to, as an event that has the potential to cause harm, but didn't. Incident is then regarded as a synonym for a near-miss event. These differences in terminology and definitions have to be taken into account when browsing through safety literature or when looking into accident investigation techniques.
The definition of an accident at work in the context of Workers' Compensation Systems
In the context of Workers' Compensation Systems accidents at work are regarded from the perspective of compensating the victim. Usually the term occupational accident is used and the definition contains the elements that allow determining whether or not the victim of an injury at work can claim compensation from the Workers' Compensation Systems.
The standard definition of occupational accident contains the following elements:
- fortuitous, sudden, or unexpected external event;
- during working hours/on the way to and back from the workplace;
- arising out of work performed in the course and the scope of employment;
- bodily harm;
- causal link between the event and the harm.
The fact that occupational accidents are fortuitous, sudden, unexpected external events allows making a distinction between accidents and diseases. Diseases are usually caused by a process extended over a longer period of time and not by a sudden event. Although this distinction seems straightforward it is not always the case. For instance, back problems can be the result from continuous exposure or be linked to a sudden event.
Occupational accidents occur during working hours and/or on the way to and from the workplace. In a broad sense occupational accidents also include commuting accidents. However, some Workers' Compensation Systems exclude this type of accidents.
The definition of an occupational accident also includes the fact that the accident has to arise out of work performed in the course and the scope of employment. This criterion often leads to discussions about accidents during activities in the workplace where the link with the scope of employment is somewhat questionable e.g. during excursions, doing private work or business at the workplace, etc. The criterion injury usually comprises not only bodily harm, but also psychic problems caused by an accident.
Finally, the concept of an occupational accident is based on the fact that there has to be a causal link between the event and the injury. Only direct consequences of the occupational accident can be compensated. Thus, when a pre-existing disease is aggravated or accelerated by an accident, compensation is payable only for what is reasonably attributable to the accident.
The definition of an accident in the context of statistical data
Although statistical data on accidents at work are often based on data provided by Workers' Compensation Systems, the definition has to be considered in a different way. The purpose is not to determine whether or not the victim has to be compensated but whether or not the event has to be recorded as an accident at work. The definition used in the European Community is developed by Eurostat in the framework of ESAW, European Statistics on Accidents at Work.
An accident at work is defined as a discrete occurrence in the course of work which leads to physical or mental harm. This includes cases of acute poisoning and wilful acts of other persons, as well as accidents occurring during work but off the company’s premises, even those caused by third parties. It excludes deliberate self-inflicted injuries, accidents on the way to and from work (commuting accidents), accidents having only a medical origin and occupational diseases.
The phrase in the course of work means whilst engaged in an occupational activity or during the time spent at work. This includes cases of road traffic accidents in the course of work.
A fatal accident is defined in ESAW as an accident leading to the death of a victim within one year of the accident. A commuting accident is defined as an accident that occurs during the normal journey between the home, the place of work and the usual place where meals are taken. Only accidents at work with an absence of more than three calendar days are included in the ESAW data. This means that an accident at work is included in the ESAW database if the person is unfit for work for more than three days, including Saturdays, Sundays or other days where the person is not usually working.
Causes of accidents at work: accident models
Prevention of accidents at work focuses on the causes of accidents: what are the causes lying underneath the event of an accident (or incident). Insight in the causes is essential to prevent future (similar) accidents. Therefore, revealing all the causes leading up to an event of an accident is the basis of investigation and analysis. Accident causation models provide a theoretical basis for explaining how accidents at work occur.
A well-known accident causation model is certainly the domino theory of Heinrich. Heinrich captured the accident sequence in five factors portrayed as domino blocks. It is a linear accident sequence of preceding factors leading up to the accident and resulting in an injury. The removal of a domino block – preventive action – results in the fact that the accident will not happen. The domino theory has been updated since by several authors and still forms the basis of many accident investigation techniques. These models are referred to as sequential accident models.
Other models have been developed since, for instance the Swiss cheese model of James Reason (figure 2). The Swiss cheese model shows several layers or barriers between management decision-making and accidents and incidents. Each of the barriers has holes and accidents or incidents occur when the holes in these layers align. Reason makes a distinction between active and latent failures. Latent failures find their origin in fallible decisions by high-level decision makers (and designers). Active failures are a mere symptom of latent failures.
A short overview of models and their impact on accident investigation methods can be found in Katsakiori et al. (2009). The choice of model and method has consequences for the factors and causes that are associated with accidents and incidents at work.
Statistical data on accidents at work
Data on accidents at work are available through national reporting systems (e.g. accident insurers) or through surveys. The European Working Conditions Survey (EWCS) asks respondents how many days off work due to health problems could be attributed to an accident. Therefore, only accidents with absence from work are reported in this survey. The Labour Force Survey (LFS) ad hoc module 1999 and 2007 provides data on self-reported occupational accidents in the year preceding to the administration of the survey, irrespective of whether these accidents resulted in absence from work. ESAW, the European Statistics on Accidents at Work, only include data on accidents at work with more than three days of absence from work and fatal accidents. The ESAW data are provided by national reporting systems. A report from Eurostat brings the data on accidents at work from these three sources together. The data below are based on this report.
How many accidents at work occur?
According to the LFS ad hoc module 2007 3.2% of the persons in the EU-27 of 15-64 years that worked or had worked during the past year had one or more accidents at work in the past 12 months. This percentage corresponds to 6.9 million persons in the EU-27. Road traffic accidents during work or in the course of work (excluding commuting accidents) were reported in the LFS ad hoc module 2007 by 0.3% of the persons, corresponding to 0.67 million persons in the EU-27. Road traffic accidents constituted 9.6% of all accidents at work. According to ESAW, 5580 workers in the EU-27 died in a fatal accident at work in 2007 and approximately 2.9 % of the workers had an accident at work with more than 3 days of absence.
Trends seem to indicate that accidents at work are decreasing. This trend can be linked to changes in the world of work. More women are working and accident rates are lower among women than men. Also the fact that Europe is facing an ageing workforce explains (partially) this decreasing trend since fewer accidents occur among older workers compared to young ones.
Who are the victims?
Men are more often victim of an accident at work than women. The LFS data from 2007 show 4.0% of the male workers had an accident in comparison with 2.1% of the female workers.
Young workers have more accidents than older ones. Figure 3 shows the occurrence of accidents at work in different age groups.
Sectors and activities
Figure 4 shows that accidents at work most occur in the sectors ‘agriculture, hunting and forestry’, ‘manufacturing’, and ‘construction’, particularly among men. Women in the sectors ‘health and social work’ and ‘hotels and restaurants’ had more often one or more accidents than women working in other sectors.
Comparable data can be found in the ESAW 2007 data (EU-15 without Greece). Accidents at work with more than three days of absence occurred most often in the sectors ‘mining and quarrying’ (10.0%), ‘construction’ (51%), ‘fishing’ (4.1%) and ‘agriculture’ (3.9%). The lowest occurrence was found in ‘financial intermediation’ (<1%), ‘real estate, renting and business activities’ and ‘electricity, gas and water supply’ (both 1.7%).
What are the causes?
Information on the type of accident at work and the chain of events that resulted in an accident can be found in the ESAW data. Figure 5 shows the events leading to fatal and non-fatal accidents. About 70% of nonfatal accidents at work result from loss of control, fall or physical stress. More than 40% of the fatal accidents result from loss of control. Many of these fatal injuries arise by contact with or collision with an object. In non-fatal accidents, injury was most often caused by horizontal/vertical impact with or against a stationary object (victim in motion), physical or mental stress, contact with sharp, pointed, rough or coarse material agent and struck by or collision with an object in motion.
What are the consequences?
The most obvious consequence of accidents is the fact that they result in absence from work. Statistics show that in the EU-27 of all persons aged 15-64 years that work or worked during the past 12 months 2.3% was on sick leave for at least one day due to an accident at work. This corresponds to approximately 5.0 million persons in the EU-27. Prolonged sick leave (for one month or more) was reported by 22.0%, which corresponds to 0.7% of the persons that work or worked during the past 12 months, and to 1.5 million persons in the EU-27. Older workers with accidents more often experience prolonged absence from work than younger workers.
The most common types of injury that result from accidents are wounds and superficial injuries, and dislocations, sprains and strains (figure 6). Injuries are most often located on the upper extremities, followed by the lower extremities.
- ↑Bird, F., Germain, G., A new horizon in accident prevention and cost improvement, New York, 1966.
- ↑OHSAS 18001 Occupational Health and Safety Management Systems Requirements Standard, 2007, http://www.ohsas-18001-occupational-health-and-safety.com
- ↑HSE – Health and Safety Executive, Investigating accidents and incidents. A workbook for employers, unions, safety representatives and safety professionals, UK, 2004.
- ↑Heinrich, H., Industrial Accident Prevention, fourth edition, New York, 1959, first edition, 1931.
- ↑HSE – Health and Safety Executive, Factoring the human into safety: Translating research into practice, The development and evaluation of a human factors accident and near miss reporting form for the offshore oil industry, volume 2 (of 3), 2003.
- ↑Katsakiori, P., Sakellaropoulos, G., Manatakis, E., Towards and evaluation of accident investigation methods in terms of their alignment with accident causation models, Safety Science, vol. 47, 2009, pp. 1007-15.
- ↑ 7.07.17.27.3Eurostat – Health and safety at work in Europe (1999-2007), A statistical portrait, August 2010. Available on: http://epp.eurostat.ec.europa.eu/portal/page/portal/product_details/publication?p_product_code=KS-31-09-290
Links to further reading
EC – European Commission, Directorate-General for Employment, Social Affairs and Equal Opportunities, Causes and circumstances of accidents at work in the EU, 2008. Available at: http://epp.eurostat.ec.europa.eu/portal/page/portal/health/documents/
Eurostat – Health and safety at work in Europe (1999-2007), A statistical portrait, August 2010. Available on: http://epp.eurostat.ec.europa.eu/portal/page/portal/product_details/publication?p_product_code=KS-31-09-290
EU-OSHA – European Agency for Safety and Health. Accident prevention. Available at: http://osha.europa.eu/en/topics/accident_prevention
Figure 1: Definitions of accident and Incident
OSH: Accident models, Accident statistics, Accidents
NACE: Growing of non-perennial crops, Growing of perennial crops, Animal production, Mixed farming, Support activities to agriculture and post-harvest crop activities, Logging, Support services to forestry, Mining of hard coal, Mining of lignite, Extraction of crude petroleum and natural gas, Mining of metal ores, Quarrying of stone, Mining support service activities, Processing and preserving of meat and production of meat products, Manufacture of dairy products, Manufacture of coke oven products, Manufacture of basic chemicals, Manufacture of pesticides and other agrochemical products, Manufacture of paints, Manufacture of soap and detergents, Manufacture of perfumes and toilet preparations, Manufacture of explosives, Manufacture of glues, Manufacture of man-made fibres, Manufacture of basic pharmaceutical products, Manufacture of pharmaceutical preparations, Manufacture of rubber and plastic products, Manufacture of basic metals, Manufacture of motor vehicles, Manufacture of other transport equipment, Repair and installation of machinery and equipment, Electric power generation, Waste collection, OFFICE CLERKS, Civil engineering, Demolition and site preparation, Passenger rail transport, Freight rail transport, Urban and suburban passenger land transport, Freight transport by road, Air transport, Hospital activities, Residential care activities, Sawmilling and planing of wood, Manufacture of products of wood, Printing of newspapers, Other printing, Binding and related services, Manufacture of articles of concrete, Manufacture of concrete products for construction purposes, Cutting, Manufacture of structural metal products, Manufacture of tanks, Forging, Treatment and coating of metals; machining, Machining, Manufacture of cutlery, Manufacture of other fabricated metal products, Manufacture of electric motors, Manufacture of domestic appliances, Manufacture of general-purpose machinery, Manufacture of other general-purpose machinery, Manufacture of agricultural and forestry machinery, Manufacture of metal forming machinery, Manufacture of other special-purpose machinery, Manufacture of furniture, Electrical, Building completion and finishing, Roofing activities, Maintenance and repair of motor vehicles, Sea and coastal passenger water transport, Inland passenger water transport, Inland freight water transport, Cleaning activities, Hairdressing and other beauty treatment, Fishing, Medical and dental practice activities, Processing and preserving of fish, Manufacture of grain mill products, Manufacture of starches and starch products, Manufacture of bakery and farinaceous products, Manufacture of beer, Manufacture of soft drinks; production of mineral waters and other bottled waters, Manufacture of paper and paper products, Hotels and similar accommodation, Holiday and other short-stay accommodation, Camping grounds
It is often helpful to see an example of an accident investigation in order to better understand how the process works. Here is a simple accident investigation case study.
This is the accident scenario:
- An employee is working on a ladder and the ladder seems to collapse.The employee falls off the ladder and breaks arm.
The investigation reveals the following details:
- Employee had worked seven 12-hour shifts in a row.
- Accident happened at end of shift.
- Employee was standing on the top step of the ladder (an unsafe action).
- The employee was approximately 10 feet above floor level.
- No fall arrest or restraint system was used.
- A ladder inspection policy is in place, but there is no evidence that the ladder has ever been inspected.
- Investigation reveals the ladder was damaged and did not provide a stable working platform in any environment.
- Interview with facility manager reveals that he did not inspect the ladder when it was due for inspection. He was aware that ladder needed to be inspected.
Factors and Possible Causes Affecting Incident
- Extended work hours may have caused employee to be tired and not clear-headed.
- Employee violated safety rule (standing on top step).
- No fall arrest system in place (required at 6 feet above floor level).
- Ladder was defective and unusable.
- Ladder had not been inspected.
- Facility manager was aware that ladder needed to be inspected but did not adhere to the existing policies and procedures for ladder inspections.
What is the Root Cause?
Which factor, if not present, could have prevented the accident?
If the facility manager had inspected the ladder and discovered the defect, the ladder would not have been used, and this accident would have been prevented.
Failure to follow established ladder inspection procedures is the root cause.
What about the Other Factors?
- Extended work hours might contribute, but there is no statistical evidence available that indicates extended work hours increase the risk of accidents.
- The safety rule violation could be a contributory cause in this accident, but not the root cause. However, if the ladder had been used properly, it is possible that the incident might have been prevented.
- •The existence of a fall arrest system may have prevented or reduced injury. This could be a contributory cause.
- The fact that the ladder was defective is certainly a contributory cause. But if the facility manager had followed procedures and removed the ladder from service, the accident would have been prevented.
The root cause of this accident could even be tracked deeper than just finding the facility manager’s failure to inspect the ladder. With more in-depth analysis, it might be found that the real cause was a failure in the system itself. Perhaps the safety system in place had no means of ensuring the facility manager actually carried out these inspections.
It is for reasons like this that accident investigations are best conducted by a team. This can ensure that as many possibilities are explored until all causes are discovered. It is easy to place blame on individuals when in actuality, the problem may be with your management systems.